An individual's diet is the sum of food and drink that one habitually consumes. Dieting is the practice of attempting to achieve or maintain a certain weight through diet. People's dietary choices are often affected by a variety of factors, including ethical and religious beliefs, clinical need, or a desire to control weight.

Not all diets are considered healthy. Some people follow unhealthy diets through habit, rather than through a conscious choice to eat unhealthily. Terms applied to such eating habits include "junk food diet" and "Western diet". Many diets are considered by clinicians to pose significant health risks and minimal long-term benefit. This is particularly true of "crash" or "fad" diets – short-term, weight-loss plans that involve drastic changes to a person's normal eating habits.

Only diets covered on Wikipedia are listed under alphabetically sorted headings.